In an Ethernet local area network (LAN), broadcasting refers to a transmission of information intended to be received by a plurality of remote devices with different addresses.
One simple broadcast algorithm is known as flooding, in which each incoming packet is sent out on every outbound line except the one it arrived on. Obviously this technique generates a large number of duplicate packets. Typically some method is used to damp or reduce the number of duplicates.
In an Ethernet (LAN), a predetermined destination address in the header of a packet identifies the packet as one to be broadcast. The level of broadcast can either be to all members of the network or to a defined group. Receiving units interpret the packet as addressed to them if a flood broadcast is detected or if a group broadcast address is detected in which they are a member. Units which are not part of the selected group reject the packet as not addressed to them.
Using flood broadcast techniques in an RF LAN environment presents difficulties. The error characteristic of the RF system, especially where the communication path is not line of sight, will probably be poorer than the error characteristic of a wired or cabled LAN. A further difficulty is presented if the RF system uses directional or sectorized antennas where only one antenna is active at a time. The best antenna utilized by a first RF unit when communicating with a second unit will typically be different than the best antenna for communicating with a third unit. Multiple antenna choices complicate the use of flood broadcasting in an RF LAN since a signal sent over a selected antenna by the transmitting unit may not be received by all other units. It would be extremely advantageous therefore to provide a packet transmission communications system and protocol capable of resolving these shortcomings.